Hello Baoquan, Thanks for your careful review. >On 06/10/14 at 04:54am, Atsushi Kumagai wrote: >> We tried to maximize the bitmap buffer to get the best performance, >> but the performance degradation caused by multi-cycle processing >> looks very small according to the benchmark on 2TB memory: >> >> https://lkml.org/lkml/2013/3/26/914 >> >> This result means we don't need to make an effort to maximize the >> bitmap buffer, it will just increase the risk of OOM. >> >> This patch sets a small fixed value (4MB) as a safety limit, >> it may be safer and enough in most cases. >> >> Signed-off-by: Atsushi Kumagai <kumagai-atsushi at mxc.nes.nec.co.jp> >> --- >> makedumpfile.c | 17 ++++++++++------- >> 1 file changed, 10 insertions(+), 7 deletions(-) >> >> diff --git a/makedumpfile.c b/makedumpfile.c >> index b8f1ec4..c23667b 100644 >> --- a/makedumpfile.c >> +++ b/makedumpfile.c >> @@ -8946,13 +8946,15 @@ out: >> >> >> /* >> - * Choose the lesser value of the two below as the size of cyclic buffer. >> - * - the size enough for storing the 1st/2nd bitmap for the whole of vmcore >> - * - 80% of free memory (as safety limit) >> + * Choose the lesser value of the three below as the size of cyclic buffer. > ~~~~~ typo, it should be less. I'll fix it. >> + * - the size enough for storing the 1st or 2nd bitmap for the whole of vmcore >> + * - 4MB as sufficient value >> + * - 60% of free memory as safety limit >> */ >> int >> calculate_cyclic_buffer_size(void) { >> unsigned long long limit_size, bitmap_size; >> + const unsigned long long maximum_size = 4 * 1024 * 1024; >> >> if (info->max_mapnr <= 0) { >> ERRMSG("Invalid max_mapnr(%llu).\n", info->max_mapnr); >> @@ -8960,17 +8962,18 @@ calculate_cyclic_buffer_size(void) { >> } >> >> /* >> - * We should keep the size of cyclic buffer within 80% of free memory >> - * for safety. >> + * At least, we should keep the size of cyclic buffer within 60% of >> + * free memory for safety. >> */ >> - limit_size = get_free_memory_size() * 0.8; >> + limit_size = get_free_memory_size() * 0.6; >> bitmap_size = info->max_mapnr / BITPERBYTE; >> >> /* if --split was specified cyclic buffer allocated per dump file */ >> if (info->num_dumpfile > 1) >> bitmap_size /= info->num_dumpfile; >> >> - info->bufsize_cyclic = MIN(limit_size, bitmap_size); >> + /* 4MB will be enought for performance according to benchmarks. */ > ~~~~~~~~ >There's a typo, here should be enough. I'll fix it. Thanks Atsushi Kumagai >> + info->bufsize_cyclic = MIN(MIN(limit_size, maximum_size), bitmap_size); >> >> return TRUE; >> } >> -- >> 1.9.0 >> >> _______________________________________________ >> kexec mailing list >> kexec at lists.infradead.org >> http://lists.infradead.org/mailman/listinfo/kexec
